One oral medical appliance which is typical of the kind to which the invention relates is the endoscopic mouth guard. This is essentially a short, right tube with somewhat flared or flanged ends, which is placed between the patient's lips and front teeth during gastroscopy to provide a safe and unobstructed passage for the endoscope. One such guard, characterised by its soft outer surface, is described and illustrated in U.S. Pat. No. 4,640,273 to F. R. Greene et al.
Another typical appliance of the kind in question is the so-called Guedel airway, which is used during recovery from anaesthesia, and comprises a curved tube adapted to be inserted partly into the mouth, through which the patient may breathe, and which is shaped to prevent the patient's tongue from falling into and blocking his or her windpipe.
It has been known for some time that patients who undergo endoscopic or other procedures requiring sedation frequently undergo hypoxia, that is to say an undesirable fall in the oxygen saturation level of the blood. The level of hypoxia may be minor and, although undesirable, deemed to be tolerable. On the other hand it may be quite profound. Indeed, in elderly patients or those with compromised circulatory or pulmonary systems, the hypoxia induced by sedation and the physical presence in the windpipe of an endoscope can precipitate cardiac or respiratory arrest. Likewise the blood oxygen level may fall unduly during recovery from anaesthesia.
Thus, even though oral medical appliances of the kind in question are normally annular or tubular so that the patient may breathe through the open mouth, there is sometimes a need to administer oxygen to a patient fitted with such an appliance.
Presently used apparatus for supplying oxygen to a patient to lift the blood oxygen level comprise face masks, which cover the mouth and nose, and nasal prongs. The use of a mask is often quite impracticable when, for example during gastroscopy, the procedure requiring use of the appliance also requires unhindered access to the oral cavity. Furthermore, most conscious patients, even if sedated, find nasal prongs uncomfortable or otherwise objectionable and their use sometimes causes internal bruising or abrasion.
Therefore, conventional means for administering oxygen to a patient fitted with an oral appliance are often unsatisfactory or inconvenient.